Weights and Measurements

A kilogram per milliliter (kg/ml) is a derived metric SI (System International) measurement unit of density used to measure volume in milliliters in order to estimate weight or mass in kilograms[...]

The frequency is defined as an interval of time, during which a physical system, e.g. electrical current or a wave, performs a full oscillation and returns to its original momentary state, in both sign (direction) and in value, is called the oscillation period of this physical system.[...]